1. Field of the Invention
The present invention relates to a magnetic recording and reproducing apparatus such as a VTR (Video Tape Recorder), and in particular, to a magnetic recording and reproducing apparatus performing a slow-motion reproduction so as to reproduce a higher quality of image.
2. Description of the Related Art
In recent years, a magnetic recording and reproducing apparatus has been used not only in executing normal recording and reproducing operations but also in analyzing an image or producing a software tape through a special reproducing process, which has also accompanied a growing trend of attaching importance to the quality of a specially reproduced image.
In a magnetic recording and reproducing apparatus most widely used using a magnetic tape (the magnetic recording and reproducing apparatus is referred to as a VTR hereinafter), a magnetic tape is wound around a rotating drum mounted together with magnetic heads, and a video signal is recorded onto a video track inclined at a specified angle with respect to the longitudinal direction of a magnetic tape. Such a VTR is referred to as a helical scan type VTR hereinafter.
When a slow-motion reproduction is executed in the helical scan type VTR, the inclination of a recorded video track does not coincide with a scanning trace of the magnetic head. This results in a deviation or shift amount on the time of a video signal, or a deteriorated signal-to-noise ratio in a part of the resulting image. Therefore, in order to obtain a stabilized slow-motion image in a simpler manner, it is required to repeat reproduction of a still image by intermittently feeding the magnetic tape periodically, or periodically stopping the moved magnetic tape. Further, in order to obtain a perfect slow-motion image having a higher quality, it is required to move the magnetic head mounted on the rotating drum in a direction perpendicular to the direction of rotation of the rotating drum and to effect control so as to correctly scan the recorded video track on the magnetic tape.
FIG. 16 shows a reproducing system of a conventional helical scan type VTR having a head driving mechanism 1605 for moving the magnetic head.
Referring to FIG. 16, 1601 denotes a magnetic tape, and the reproducing system of the conventional VTR comprises a magnetic head 1602, a preamplifier 1603, a video signal reproducing circuit 1604, the head driving mechanism 1605, a head driving circuit 1606, a level detecting circuit 1607, and a controller 1608.
When a slow-motion reproduction is executed in the conventional VTR shown in FIG. 16, a RF (radio frequency) video signal recorded on the magnetic tape 1601 is reproduced by the magnetic head 1602, and the resulting reproduced RF video signal is amplified by the preamplifier 1603, and then, the amplified RF video signal is demodulated so as to obtain a reproduced video signal. On the other hand, the level detecting circuit 1607 converts the RF video signal outputted from the preamplifier 1603 into an output signal representing the signal level of the RF video signal. Then the controller 1608 generates a control signal for controlling the height of the magnetic head 1602 to be arranged so that the level of the output signal from the level detecting circuit 1607 becomes the maximum, and outputs the control signal for therefor through the head driving circuit 1606 to the head driving mechanism 1605 so as to move the magnetic head 1602 mounted on the rotating drum in a direction perpendicular to the direction of rotation of the drum by means of the head driving mechanism 1605 mounted with the magnetic head 1602. Consequently, the magnetic head 1602 correctly scan the recorded video track on the magnetic tape 1601.
Since the magnetic head 1602 is moved by a special mechanism in the above-mentioned conventional VTR, the cost of the conventional VTR becomes higher, and also it becomes difficult to heighten the reliability thereof. Further, when a slow-motion reproduction is executed in the simple way of intermittently feeding the magnetic tape, noise is generated in the slow-motion reproduction of the reverse direction. Furthermore, since the intermittent feed of the magnetic tape cannot be performed so quickly, there is a limitation in the speed to about one fifth of the normal reproduction speed.